U.S. patent number 7,954,401 [Application Number 11/553,651] was granted by the patent office on 2011-06-07 for method of assembling a drill bit with a jack element.
This patent grant is currently assigned to Schlumberger Technology Corporation. Invention is credited to Joe Fox, David R. Hall, Francis E. Leany, Tyson J. Wilde.
United States Patent |
7,954,401 |
Hall , et al. |
June 7, 2011 |
Method of assembling a drill bit with a jack element
Abstract
A method of assembling a drill bit with a jack element that
includes obtaining a bit body intermediate a shank and a working
face, with the working face including a plurality of blades having
of at least one cutting element and a receptacle formed proximate a
center of the working face. The method further includes attaching a
pocket having a central hollow within the receptacle, and securing
the jack element within the central hollow with a press fit such
that the centerline of the jack element is substantially coaxial
with the axis of rotation of the drill bit.
Inventors: |
Hall; David R. (Provo, UT),
Leany; Francis E. (Salem, UT), Fox; Joe (Spanish Fork,
UT), Wilde; Tyson J. (Spanish Fork, UT) |
Assignee: |
Schlumberger Technology
Corporation (Houston, TX)
|
Family
ID: |
39364002 |
Appl.
No.: |
11/553,651 |
Filed: |
October 27, 2006 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
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US 20080099243 A1 |
May 1, 2008 |
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Current U.S.
Class: |
76/108.2;
76/108.1 |
Current CPC
Class: |
E21B
10/54 (20130101) |
Current International
Class: |
B21K
5/04 (20060101) |
Field of
Search: |
;76/108.1,108.2,108.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
PCT/US06/43125, International Search Report dated May 27, 2008.
cited by other .
PCT/US06/43125, Written Opinion dated May 27, 2008. cited by other
.
PCT/US07/64539, International Search Report and Written Opinion
dated Jun. 16, 2008. cited by other .
PCT/US07/64544, International Search Report dated Aug. 5, 2008.
cited by other .
PCT/US07/64544, Written Opinion dated Aug. 5, 2008. cited by
other.
|
Primary Examiner: Payer; Hwei-Siu C
Attorney, Agent or Firm: Holme Roberts & Owens LLP
Claims
What is claimed is:
1. A method of assembling a drill bit with a jack element,
comprising: obtaining a drill bit that includes: a shank; and a bit
body attachable to said shank at a first end and having a working
face at a second end opposite said first end, said working face
including a receptacle formed proximate a center of said working
face; shaping said receptacle to substantially align a centerline
of said receptacle with an axis of rotation of said drill bit;
attaching a pocket within said receptacle; shaping a central hollow
of said pocket to substantially align a centerline of said central
hollow with said axis of rotation of said drill bit; and securing a
jack element within said central hollow of said pocket such that
said jack element is substantially coaxial with said axis of
rotation of said drill bit.
2. A method of assembling a drill bit with a jack element,
comprising: obtaining a drill bit that includes: a shank; and a bit
body attachable to the shank at a first end and having a working
face at a second end opposite the first end and a receptacle formed
proximate a center of the working face; attaching a pocket within
the receptacle; shaping a central hollow of the pocket to align a
centerline of the central hollow with an axis of rotation of the
drill bit; and securing a jack element within the central hollow of
the pocket with a press fit such that the jack element is
substantially coaxial with the axis of rotation of the drill
bit.
3. The method of claim 2, further comprising forming a channel
extending from an interior surface of the receptacle to a bore of
the bit body.
4. The method of claim 2, further comprising forming a groove into
an inner surface of the central hollow of the pocket.
5. The method of claim 2, wherein the receptacle formed into the
working face is substantially coaxial with the axis of rotation
before machining to accept the pocket.
6. The method of claim 2, wherein the working face further
comprises at least one cutting element disposed proximate the axis
of rotation.
7. The method of claim 6, wherein an outermost portion of the at
least one cutting element proximate the axis of rotation extends a
first distance from the working face, and wherein securing the jack
element further comprises securing the jack element such that a
distal end of the jack element extends a second distance from the
working face that is between 25% and 125% greater than the first
distance.
8. The method of claim 6, wherein the at least one cutting element
is pre-flatted to allow insertion of the pocket into the
receptacle.
9. The method of claim 8, further comprising grinding a portion of
the at least one cutting element disposed proximate the axis of
rotation to allow insertion of the pocket into the receptacle.
10. The method of claim 2, wherein a material forming the pocket is
selected from the group consisting of aluminum, titanium, steel,
mild steel, hardened steel, stainless steel and a metallic
alloy.
11. The method of claim 2, wherein the pocket comprises an annular
wall thickness not less than 0.125 inches.
12. The method of claim 2, wherein the central hollow of the pocket
comprises a diameter not less than 0.75 inches.
13. The method of claim 2, wherein attaching the pocket within the
receptacle comprises brazing the pocket into the receptacle.
14. The method of claim 13, wherein brazing the pocket into the
receptacle further comprises brazing with a brazing alloy filler
selected from the group consisting of copper, silver, nickel,
aluminum, gold, tin, zinc, a refractory metal, carbide, tungsten
carbide, niobium, titanium, platinum and molybdenum.
15. The method of claim 2, wherein the jack element comprises a
material selected from the group consisting of gold, silver, a
refractory metal, carbide, tungsten carbide, cemented metal
carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt,
nickel, iron and cubic boron nitride.
16. The method of claim 2, wherein the press fit between the jack
element and the central hollow of the pocket comprises an
interference between 0.0020 and 0.0025 inches.
17. The method of claim 2, wherein a distal end of the jack element
includes a layer of abrasion resistant material selected from the
group consisting of natural diamond, polycrystalline diamond, boron
nitride, and, tungsten carbide.
18. The method of claim 17, wherein the layer of abrasion resistant
material comprises a thickness of 0.5 mm to 4.0 mm.
19. The method of claim 2, wherein the jack element includes a
distal end having a domed, rounded, semi-rounded, conical, flat, or
pointed geometry.
20. The method of claim 2, wherein the jack element comprises a
polygonal shaft.
21. A method of assembling a drill bit with a jack element,
comprising: obtaining a drill bit that includes: a shank; and a bit
body attachable to said shank at a first end and having a working
face at a second end opposite said first end, said working face
including a receptacle formed proximate a center of said working
face; attaching a pocket having a central hollow within said
receptacle; shaping said central hollow of said pocket to align a
centerline of said central hollow with an axis of rotation of said
drill bit; and securing a jack element within said central hollow
of said pocket such that a centerline of said jack element is
substantially coaxial with said axis of rotation of said drill
bit.
22. The method of claim 21, wherein said working face further
comprises at least one cutting element disposed proximate said axis
of rotation.
23. The method of claim 22, further comprising grinding a portion
of said at least one cutting element to allow insertion of said
pocket into said receptacle.
Description
BACKGROUND OF THE INVENTION
This invention relates to drill bits, specifically drill bit
assemblies for use in oil, gas and geothermal drilling. Drill bits
are continuously exposed to harsh conditions during drilling
operations in the earth's surface. Bit whirl in hard formations for
example may result in damage to the drill bit and reduce
penetration rates. Further loading too much weight on the drill bit
when drilling through a hard formation may exceed the bit's
capabilities and also result in damage. Too often unexpected hard
formations are encountered suddenly and damage to the drill bit
occurs before the weight on the drill bit may be adjusted. When a
bit fails it reduces productivity resulting in diminished returns
to a point where it may become uneconomical to continue drilling.
The cost of the bit is not considered so much as the associated
down time required to maintain or replace a worn or expired bit. To
replace a bit requires removal of the drill string from the bore in
order to service the bit which translates into significant economic
losses until drilling can be resumed.
The prior art has addressed bit whirl and weight on bit issues.
Such issues have been addressed in the U.S. Pat. No. 6,443,249 to
Beuershausen, which is herein incorporated by reference for all
that it contains. The '249 patent discloses a PDC-equipped rotary
drag bit especially suitable for directional drilling. Cutter
chamfer size and backrake angle, as well as cutter backrake, may be
varied along the bit profile between the center of the bit and the
gage to provide a less aggressive center and more aggressive outer
region on the bit face, to enhance stability while maintaining side
cutting capability, as well as providing a high rate of penetration
under relatively high weight on bit.
U.S. Pat. No. 6,298,930 to Sinor which is herein incorporated by
reference for all that it contains, discloses a rotary drag bit
including exterior features to control the depth of cut by cutters
mounted thereon, so as to control the volume of formation material
cut per bit rotation as well as the torque experienced by the bit
and an associated bottomhole assembly. The exterior features
preferably precede, taken in the direction of bit rotation, cutters
with which they are associated, and provide sufficient bearing area
so as to support the bit against the bottom of the borehole under
weight on bit without exceeding the compressive strength of the
formation rock.
U.S. Pat. No. 6,363,780 to Rey-Fabret which is herein incorporated
by reference for all that it contains, discloses a system and
method for generating an alarm relative to effective longitudinal
behavior of a drill bit fastened to the end of a tool string driven
in rotation in a well by a driving device situated at the surface,
using a physical model of the drilling process based on general
mechanics equations. The following steps are carried out: the model
is reduced so to retain only pertinent modes, at least two values
Rf and Rwob are calculated, Rf being a function of the principal
oscillation frequency of weight on hook WOH divided by the average
instantaneous rotating speed at the surface, Rwob being a function
of the standard deviation of the signal of the weight on bit WOB
estimated by the reduced longitudinal model from measurement of the
signal of the weight on hook WOH, divided by the average weight on
bit defined from the weight of the string and the average weight on
hook. Any danger from the longitudinal behavior of the drill bit is
determined from the values of Rf and Rwob.
U.S. Pat. No. 5,806,611 to Van Den Steen which is herein
incorporated by reference for all that it contains, discloses a
device for controlling weight on bit of a drilling assembly for
drilling a borehole in an earth formation. The device includes a
fluid passage for the drilling fluid flowing through the drilling
assembly, and control means for controlling the flow resistance of
drilling fluid in the passage in a manner that the flow resistance
increases when the fluid pressure in the passage decreases and that
the flow resistance decreases when the fluid pressure in the
passage increases.
U.S. Pat. No. 5,864,058 to Chen which is herein incorporated by
reference for all that is contains, discloses a downhole sensor sub
in the lower end of a drillstring, such sub having three
orthogonally positioned accelerometers for measuring vibration of a
drilling component. The lateral acceleration is measured along
either the X or Y axis and then analyzed in the frequency domain as
to peak frequency and magnitude at such peak frequency. Backward
whirling of the drilling component is indicated when the magnitude
at the peak frequency exceeds a predetermined value. A low whirling
frequency accompanied by a high acceleration magnitude based on
empirically established values is associated with destructive
vibration of the drilling component. One or more drilling
parameters (weight on bit, rotary speed, etc.) is then altered to
reduce or eliminate such destructive vibration.
BRIEF SUMMARY OF THE INVENTION
In one aspect of the invention the method has steps for forming a
drill bit with an axis of rotation having a bit body intermediate a
shank and a working face. The bit body has a working face with a
plurality of blades that may extend outward from the bit body. The
working face may comprise at least one cutting element disposed
along the blades. A receptacle in the working face of the drill bit
may be formed to accept a pocket that is coaxial to the axis of
rotation. A jack element that is disposed within the pocket and
extends from the working face of the drill bit within a range
defined by the at least one cutting element proximate the axis of
rotation.
In some embodiments the drill bit may be force balanced. The pocket
may be brazed and then machined using a mill or lathe to ensure
that the jack element is substantially coaxial with the axis of
rotation when attached to the pocket. Portions of the at least one
cutting element proximate the axis of rotation may be pre-flatted
or ground flat in order to accommodate the jack element. The jack
element may be brazed, press fit, bonded, welded or threaded into
the pocket and protrude from the working face within a range
defined by the cutting surface of the at least one cutting element
proximate to the axis of rotation. Materials suitable for the at
least one cutting element or jack element may be selected from the
group consisting of diamond, polycrystalline diamond, natural
diamond, synthetic diamond, vapor deposited diamond, silicon bonded
diamond, cobalt bonded diamond, thermally stable diamond,
polycrystalline diamond with a binder concentration of 1 to 40
weight percent, infiltrated diamond, layered diamond, polished
diamond, course diamond, fine diamond cubic boron nitride,
chromium, titanium, aluminum, matrix, diamond impregnated matrix,
diamond impregnated carbide, a cemented metal carbide, tungsten
carbide, niobium, or combinations thereof. The jack element may
have a distal end with a blunt geometry with a generally
hemi-spherical shape, a generally flat shape, a generally conical
shape, a generally round shape, a generally asymmetric shape, or
combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective diagram of an embodiment of a drill bit
assembly with a jack element.
FIG. 2 is a cross sectional diagram of an embodiment of a drill bit
assembly with a jack element.
FIG. 3 is a perspective diagram of another embodiment of drill bit
assembly depicting a force balanced bit.
FIG. 4 is a cross sectional diagram of another embodiment of a
drill bit assembly depicting at least one cutting element that is
pre-flattened and a jack element.
FIG. 5 is a perspective diagram of an embodiment of drill bit
assembly depicting a method of brazing.
FIG. 6 is a cross sectional diagram of another embodiment of a
drill bit assembly depicting a method of machining the pocket using
a mill.
FIG. 7 is a cross sectional diagram of another embodiment of a
drill bit assembly with a protruding jack element.
FIG. 8 is a cross sectional diagram of another embodiment of a
drill bit assembly with a channel.
FIG. 9 is a perspective diagram of an embodiment of a pocket.
FIG. 10 is a diagram of a method for assembling a drill bit with a
jack element.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
FIGS. 1 and 2 disclose a drill bit 100 of the present invention.
The drill bit 100 is formed to comprise a shank 110 which is
adapted for connection to a downhole tool string. A bit body 120 is
formed and attached to the shank 110 and comprises an end which
forms a working face 124. A receptacle 140 is formed or molded into
the working face 124 of the drill bit 100 and may be disposed
substantially coaxial with the axis 122 of rotation of the drill
bit 100. A pocket 150 which may comprise a material selected from
the following including aluminum, titanium, steel, mild steel,
hardened steel, stainless steel, a metallic alloy or combinations
thereof, may be brazed within the receptacle 140 of the working
face 124.
In some embodiments a centerline 142 of the receptacle 140 may not
be substantially coaxial with the axis 122 of rotation of the drill
bit 100. In other embodiments the working face 124 may form a
raised buttress that encapsulates the receptacle 140 and protrudes
from the center of the working face 124. A channel 128 may be
formed and may extend from the receptacle 140 to a bore 126 within
a portion of the bit body 120. The channel 128 may allow air to
enter or exit the receptacle 140 when the jack element 170 is
inserted or removed and prevent a suction effect.
A jack element 170 that may comprise of a material selected from
the group consisting of gold, silver, a refractory metal, carbide,
tungsten carbide, cemented metal carbide, niobium, titanium,
platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron
nitride, and combinations thereof, may be press fit within the
pocket 150 such that it may be substantially coaxial with an axis
122 of rotation of the drill bit 100. The working face 124 may also
comprise a plurality of blades 130 that are formed to extend
outwardly from the bit body 120, each of which may also comprise at
least one cutting element 134. Preferably the drill bit 100 will
have between three and seven blades 130. In other embodiments the
at least one cutting element 134 proximate the axis 122 of rotation
of the drill bit 100 may also be pre-flatted or ground flat to
accommodate the jack element 170. A plurality of nozzles 144 may
also be fitted into recesses 146 formed or molded into the working
face 124.
The incorporation of the pocket 150 allows the jack element 170 to
be aligned with the axis 122 of rotation of the bit 100. Brazing
requires heating, which causes the receptacle 140 to expand and
then shrink when cooling. This shrinking may reorient the
receptacle 140 such that it is angled or misaligned from the axis
122. By brazing the pocket 150 formed from shapeable material, such
as steel, into the receptacle, and then shaping the pocket such
that it is truly aligned with the axis 122 of rotation of the drill
bit 100 allows the jack element to be press fit into the receptacle
such that the centerline of the jack element is aligned with the
axis of rotation. It has been found the jack element's life can
greatly increase the closer the jack element is aligned with the
axis of rotation of the bit. It has also been found that
misalignment, such as that caused by shrinking induced during the
cooling stage of brazing, can greatly reduce the life of the jack
element.
Another advantage to press fitting a jack element 170 into the
pocket 150 is to avoid brazing the jack element directly. The jack
element may be subjected to high loads downhole and in some cases
subjecting the jack to the heating and cooling required during
brazing may damage the jack element.
FIG. 3 discloses a diagram of another embodiment of a drill bit 200
depicting the placement of the at least one cutting element 234
around the blades 230 so that the drill bit 200 may be force
balanced. Vector calculations 238 may be used to calculate the
placement the cutting elements 234 around the blades 230 so that
the forces acting on the body 220 of the drill bit 200 while
engaged in boring through the earth's formations are distributed
substantially evenly over the working face 224 of the bit.
Specifically the vector calculations 238 may be used to calculate
horizontal torque and vertical weight on bit forces acting on the
face of each cutting element 234. The calculations may then be used
to determine the horizontal components of those forces to determine
the net force imbalance. The cutting elements 234 may then be
disposed around the blades 230 to help reduce the net force
imbalance so that the bit has minimal side force when drilling.
Mathematically this is represented by the equations;
SFx=Fx1+Fx2+Fx3+Fx4+Fx5=0 SFy=Fy1+Fy2+Fy3+Fy4+Fy5=0 This embodiment
has proven to increase overall durability of drill bits and assists
to prolong the life of the cutting elements 234. In other
embodiments the vector calculations 238 may also be manipulated to
determine optimal positioning of the jack element 270 before the
receptacle 240 is formed into the working face 224 such that the
receptacle 240 may be substantially coaxial to the axis 222 of
rotation without adversely affecting the balance of the drill bit
200. For instance, the receptacle can be formed or molded into the
working face and substantially coaxial with the axis of rotation of
the drill bit prior to machining the receptacle to accept the
pocket.
FIG. 4 discloses a cross section of an embodiment of the drill bit
300 depicting how one or more cutting elements 334 disposed
proximate the axis 322 of rotation of the drill bit 300 may be
machined pre-flat during fabrication or ground flat after
fabrication of the working face 324 such that there is sufficient
space to install or accommodate both the pocket 350 and the jack
element 370 within the receptacle 340 such that a centerline 372 of
the jack element 370 may be substantially coaxial with the axis 322
of rotation of the drill bit 300. The cutting elements 334 may
comprise of a polycrystalline diamond compact formed through the
HPHT process with a diameter up to 2 inches and a thickness of at
least 0.250 inches. In some embodiments, the distal end 374 of the
jack element 370 includes a cubic boron nitride or other ceramic
compact 380 to prevent wear.
FIG. 5 discloses a cross section of an embodiment of the drill bit
400 wherein the pocket 450 may be brazed into the receptacle 440 of
the drill bit 400 using an alloy rod 462 to provide filler 460 to
bond the two elements together. In other embodiments the filler 460
may also comprise of a tape, foil or preform. In other embodiments,
the pocket 450 can be attached into the receptacle 440 through oven
brazing. The filler 460 may be selected from the group consisting
of copper, silver, nickel, aluminum, gold, tin, zinc, a refractory
metal, carbide, tungsten carbide, niobium, titanium, platinum,
molybdenum or combinations thereof. The embodiment however, may
first comprise the steps of cleaning the pocket and/or receptacle
using steam, a chemical bath, a degreasing solvent, an abrasive
cloth, stainless steel wire brush or combinations thereof, after
which flux may be applied to help prevent oxides forming which
could weaken the joint during and after heating. The pocket 450
and/or receptacle 440 may then be heated separately or together to
at least 1200.degree. F. before the two are bonded together using
the filler 460. The channel 428 may allow air to enter or exit the
receptacle 440 when the jack element 470 and/or pocket 450 is
inserted or removed and prevent a suction effect. In some
embodiments, the channel 428 may also be formed in the pocket, or
just in the receptacle.
FIG. 6 discloses a cross section of an embodiment of the drill bit
500 having a pocket 550 with an annular thickness 556 preferably
not less than 0.125 inches and an initial bore or central hollow
552 with an inner diameter 558 of preferably not less than 0.75
inches. The diagram further discloses an embodiment wherein a
portion 566 up to 0.060 inches of the annular thickness 556 may be
removed by a mill 590 or lathe (not shown) such that the centerline
554 of the resultant bore or central hollow 552 may be realigned to
be substantially coaxial with the axis 522 of rotation of the drill
bit 500 for receiving the jack element (not shown).
FIG. 7 discloses a cross section of an embodiment of the drill bit
600 having a jack element 670 that may be press fit into the pocket
650 such that the jack element protrudes from the working face 624.
The jack element 670 may comprise an interference of between 0.0008
and 0.0050 inches with the bore or central hollow of the pocket
650. The embodiment also depicts the distal end 674 of the jack
element 670 protruding 125% the height 636 of the at least one
cutting element 634 that is disposed proximate the axis 622 of
rotation of the drill bit 600, and comprise a domed, rounded,
semi-rounded, conical, flat, or pointed geometry. In other
embodiments however, the jack element 670 may protrude between 25%
and 125% the height 636 of the one or more cutting elements 634
disposed proximate the axis 622 of rotation of the drill bit
600.
The distal end 674 of the jack element 670 may further comprise a
generally non-planar interface 678 disposed between a layer or
coating of abrasion resistant material 680. The abrasion resistant
material may comprise a thickness of between 0.5 and 4.0 mm. The
abrasion resistant material 680 may further comprise a material
selected from the group of materials that includes natural diamond,
polycrystalline diamond, boron nitride, tungsten carbide or
combinations thereof, and which tend to display high wear resistant
properties. In a preferred embodiment the abrasion resistant
material 680 is sintered to the distal end 674 of the jack element
670; however the abrasion resistant material 680 may alternatively
be brazed, press fit, welded, threaded or otherwise attached to the
jack element 670.
FIG. 8 discloses another embodiment of the drill bit 700 wherein
the channel 728 may be formed to extend from the receptacle 740
and/or sleeve 750 into a portion of the nozzle chamber 748.
FIG. 9 is a perspective diagram of an embodiment of a polygonal
pocket 950, which is adapted to receive a polygonal-shaped shaft of
a jack element. A groove 968 is formed in the pocket 950 which
allows the polygonal-shaft jack element to be press fit into the
pocket without creating a suction effect. The groove 968 may run
the entire length 964 of the pocket or just a portion of the
length. In other embodiments, the groove may form a spiral. The
polygonal pocket may be closed or open ended on a proximal end 951
of the pocket. The polygonal pocket 950 may be brazed, press fit,
or otherwise attached into the receptacle of the working face of
the bit. While the embodiment of FIG. 9 discloses a polygonal
pocket 950 with an inner and outer diameter 958, 959 with generally
polygonal shape, in some embodiments, only inner diameter 958 of
the pocket comprises a generally polygonal shape, while in other
embodiments only the outer diameter 959 of the pocket comprises a
generally polygonal shape.
A jack element with a polygonal shaft (not shown) or a pocket 950
may be better adapted to resist torque produced during drilling. In
some embodiments, a polygonal-shaft jack element may require a
lesser press fit than a jack element with a more cylindrical shaft.
In some embodiments, the pocket may comprise a more permanent
attachment to the receptacle than the attachment of the jack
element to the pocket, so that it is easier to replace the jack
element without having to replace the pocket as well. In some
embodiments, the pocket 950 may comprise a thread formed into the
inner diameter of the pocket for easy installation and removal of
the jack element. While the embodiment of FIG. 9 discloses a
generally square polygonal shape, the generally polygonal shape may
be generally triangular, hexagonal or other polygonal shapes.
FIG. 10 is a diagram of a method 1000 of assembling a drill bit
with a jack element. The method comprises the steps of obtaining
1002 a drill bit with a body intermediate a shank and a working
portion comprising one or more cutting elements and a receptacle in
the working face, and with a channel extending from the receptacle
to a bore of the bit body; grinding 1004 a cutting element disposed
proximate the axis of rotation of the drill bit to allow insertion
of a pocket into the receptacle; brazing 1006 the pocket within the
receptacle; machining 1008 a central hollow of the pocket within
the receptacle such that the centerline of the central hollow is
substantially coaxial with the axis of rotation of the drill bit;
and press fitting 1010 the jack element into the central hollow of
the pocket such that the jack element protrudes from the working
face of the drill bit.
Whereas the present invention has been described in particular
relation to the drawings attached hereto, it should be understood
that other and further modifications apart from those shown or
suggested herein, ma be made within the scope and spirit of the
present invention.
* * * * *